This book tells two stories: one about typhus and the other about the scientists plight under Nazi rule.

There are a few facts about typhus that I think everyone should know:

It is a disease known since antiquity

It is spread through body lice

It can wreak destruction in populations that don't wash their clothes regularly -- just ask Napoleon

Countermeasures against typhus were a priority for the military in the pre-antibiotic era

Given this context, you can see how typhus vaccine---invented by Rudolf Weigl--would attract the attention of the Germany military during WWII.

The enormous benefit and ingenuity needed to make the vaccine isn't the most remarkable part of the book however. What I found most remarkable was that during the Nazi occupation of Poland, when the laboratories were under strict Nazi control, heroic scientists thought to sabotage the Nazis by giving inert control vaccine to the Nazis while giving real vaccine to those in the Jewish ghettos.

Such acts really give concrete form to the definition of hero, formulated by philosopher Andrew Bernstein, as "the man who lets no obstacle prevent him from pursuing the values he has chosen."